A battery obtained by welding a lid to a casing is known in the art as an object formed by welding two joining subject members with a laser welding device. Highly accurate welding between the casing and the lid is performed to maintain a high sealing degree for the battery so that electrolyte or the like does not leak from the casing. Patent Document 1 describes one example of a technique for welding the lid and the casing of the battery.
In the technique described in Patent Document 1, when the lid (battery lid) and the casing (battery can) of the battery are welded using a laser beam, at the location where the battery is welded, a distal end portion of the lid extends beyond the edge between an open upper end surface and an outer wall surface of the casing. The laser beam is emitted to an area including the distal end portion. This at least partially fills a gap at the welded portion with a molten body of the distal end portion of the lid.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2000-21365